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    聚硅氮烷催化氰酸酯树脂聚合反应

    Polymerization Reactions of Polysilazane-Catalyzed Cyanate Esters

    • 摘要: 通过氨解法合成了两种聚硅氮烷聚合物−聚二甲基硅氮烷(PMS)和聚甲基氢硅氮烷(PHS)。采用PMS和PHS催化聚合双酚A型氰酸酯单体(BADCy),分别得到预聚物PMS-BADCy和PHS-BADCy。采用傅里叶红外光谱(FT-IR)、核磁共振波谱(NMR)等对聚硅氮烷和预聚物的结构进行了表征,研究了催化聚合反应机理,确定了预聚物的固化加工工艺,并验证了树脂固化物的性能。结果表明:聚硅氮烷可有效催化氰酸酯树脂在80 ℃发生聚合反应生成三嗪环结构,形成具有致密均相结构的固化物,其热机械性能较好、热稳定性能优异、耐湿性能良好,且聚硅氮烷催化聚合氰酸酯较纯氰酸酯树脂固化后呈现出更加优异的力学性能。预聚反应机理研究表明,聚硅氮烷催化氰酸酯树脂的聚合反应过程中形成了含有―O―Si―NH―CN结构的高活性中间体,此活性中间体可继续与―C≡N反应,生成含有―C=NH结构的二聚体或多聚体,然后经环三聚反应形成对称或不对称的三嗪环结构。

       

      Abstract: Two types of polysilazane polymers, polydimethylsilazane (PMS) and polymethylsilazane (PHS), were synthesized through ammonolysis. PMS and PHS were used to catalyze the polymerization of cyanate ester resin (BADCy), resulting in the prepolymers, PMS-BADCy and PHS-BADCy, respectively. The structures of polysilazanes and prepolymers were characterized using Fourier ransform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Catalytic polymerization mechanism and curing process of prepolymers were examined, and the properties of the resulting cured resin products were also verified. Results indicated that polysilazanes effectively catalyzed the polymerization of cyanate ester resins at 80 ℃, and catalyzed the formation of triazine ring structures in BADCy resin. Research into the prepolymerization mechanism showed that during the catalytic polymerization of cyanate ester resins by polysilazanes, highly reactive intermediates containing ―O―Si―NH―CN structures were formed. These intermediates subsequently reacted with ―C≡N to form dimers or oligomers containing ―C=NH structures, followed by cyclotrimerization to form symmetric or asymmetric triazine ring structures. The cured resin exhibited excellent thermal mechanical properties, superior thermal stability, and improved moisture resistance. The cured product exhibited a dense, homogeneous structure. Polysilazane-catalyzed cyanate ester resins showed significantly enhanced mechanical properties compared to pure cyanate ester resins. It is very promising that the reaction between ―OCN and polysilazane may be used to reduce the prepolymerization temperature and achieve controllable prepolymerization. The prepolymers have a wide processing window and exhibit a lower curing temperature and curing exothermic enthalpy when compared to BADCy.

       

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